Sen. Dianne Feinstein called on the Federal Aviation Administration to ground all Boeing 737 MAX 8 airplanes until an investigation into the Ethiopian Airlines plane crash that killed 157 people on Sunday is complete.

“Until the cause of the crash is known and it’s clear that similar risks aren’t present in the domestic fleet, I believe all Boeing 737 MAX 8 series aircraft operating in the United States should be temporarily grounded,” Feinstein said in a statement. “This aircraft model represents only a small fraction of the domestic fleet, and several other countries have already taken this important step, including China and Indonesia.”

The plane crash on Sunday near Addis Ababa, Ethiopia, follows an incident in October when a Lion Air jet, also a Boeing 737 MAX 8 aircraft, crashed into the sea off the coast of Indonesia. Feinstein said the similar airplane crashes have “raised legitimate questions about whether an unknown problem exists, which must be discovered and remedied as soon as possible.”

“Continuing to fly an airplane that has been involved in two fatal crashes within just six months presents an unnecessary, potentially life-threatening risk to the traveling public,” she said.

The FAA declined to comment on Feinstein’s request. Earlier Monday, U.S. aviation regulators said they would issue a global notice of “continued airworthiness,” for the Boeing aircraft model, signaling that the FAA is currently confident in the 737 MAX 8.